1. Field of the Invention
The present invention relates to a combustion furnace for burning a sample to be analyzed.
2. Description of Related Art
It is well known that a sample can be analyzed by burning the sample in a furnace and analyzing the gaseous ingredients emitted. It is also well known that the combustion of the sample generates a large amount of dust. Cylindrical filters have been tried for removal of this residual dust. However, the dust generated by combustion still remains a problem. Additionally, burning agents such as tungsten and tin, which may be added to promote the extraction of ingredients from the sample, increase the quantity of dust generated.
The quantity of dust generated by combustion of the sample creates problems in the system. The dust sticks to the filter, as well as to the internal areas of the combustion chamber, creating problems in that the filtration effect of the filter is lowered. Moreover, the extracted ingredients to be analyzed are adsorbed by the dust, thus lowering the accuracy of the analysis.
Accordingly, combustion furnaces for the burning of samples have been provided with a device for removing the dust stuck to inner surfaces of the filter and the furnace, as shown in FIG. 3.
FIG. 3 shows a conventional furnace for analyzing the ingredients of a sample. The furnace has a body 31 and a combustion cylinder 32 provided in the body 31. A heater 33 used for high-frequency heating is located on the periphery of a combustion cylinder 32. A crucible 34, which contains a sample to be analyzed, is placed on a holding member 35. A cylindrical filter 36 is arranged in a manner that permits the ingredients to be analyzed to travel from the combustion cylinder 32 to the outlet port 39. A cleaning rod 37 is provided that reciprocally slides and rotates in a circumferential direction within the filter 36 and the combustion cylinder 32. The cleaning rod 37, which is also used as a lance, is provided with a brush 38 mounted on an end for cleaning inner surfaces of the filter 36 and the combustion cylinder 32. A heating member 40 is provided for heating the filter 36.
In this prior art combustion furnace, the crucible 34, with the sample inside, is inserted into the combustion cylinder 32. The combustion cylinder 32 is heated by means of the heating member 33 to the point of burning the sample. The gaseous ingredients emitted are passed through the filter 36 and sent to an analyzer (not shown) through an outlet line (not shown) connected to the outlet port 39. The brush 38 is located in an upper portion inside the combustion cylinder 32 during the combustion of the sample. Dust generated by the combustion sticks to the inner surface of the combustion cylinder 32 and the filter 36.
The dust can then be removed by means of the brush 38 mounted on the end portion of the cleaning rod 37 by reciprocally sliding and rotating the cleaning rod 37 manually or by the use of a motive power (motor and the like).
The removal of the dust in the conventional combustion furnace, carried out by moving the brush 38 by means of the cleaning rod 37, presents problems. First, considerable labor is required. Second, the construction is complicated. Also, since only the inner circumferential surface of the filter 36 is scrubbed with the brush 38, it is difficult to remove the dust on an inside filament layer of filter 36. Thus, most probably part of the dust will not be removed by this method. Furthermore, since the surface of the filter 36 is varied by cleaning with the brush, repeated analysis of the waste ingredients is required.
An additional problem is presented by the fact that the brush 38 is always located within the combustion cylinder 32. This considerably complicates the construction of the interior of the furnace.